Warp unwinder for weaving looms

ABSTRACT

The invention pertains a process for warp let off from a thread shaft in a weaving loom with take-up device and in which the thread shaft is driven by an electric motor, comprising the steps of transforming the motion of a movable part of the take-up device into an electric magnitude inversely proportional to the pick density; transforming continuously the thread shaft diameter into an electric magnitude inversely proportional to such diameter; detecting and transforming at least the tension variations of the warp into an electric amplitude proportional thereto; conducting the rotary speed of said electric motor with these three electric magnitudes in such a manner that this speed remains constantly inversely proportional to the pick density and to the diameter of the thread shaft and that this speed changes in the same direction as the said tension variations of the warp, during normal operation of the loom.

United States Patent Steverlynck 3 Apr. 9, 1974 WARP UNWINDER FOR WEAVING LOOMS FOREIGN PATENTS 0R APPLICATIONS lnveflwti Bernard Charles-Louis y 9284M 6/!947 France to 139/99 leper. Belgium [73] Assignee: Weeiautomaten Picauol, n.v., leper. Primary EXami'1er-Jame5 K66 Chi B l i Attorney, Agerzr or Firm-Richards 8:. Geier {22} Filed: Feb. 22 1972 2i) A i No 228 225 {57] ABSTRACT pp i The invention pertains a process for warp let off from a thread shaft in a weaving loom with take-up device {30} Ffll'elgn pp Priority Dam and in which the thread shaft is driven by an electric Feb. 26, 1971 Belgium rrrrrrrrrrr l. 763488 motor, comprising the steps of transforming the mo- June 15 971 Belgium 76852: tion of a movable part of the take-tip device into an electric magnitude inversely proportional to the pick {52] US. Cl. r l l l r 139, M38 density; transforming continuously the thread shaft di- {51] Int. Cl 003d 49106 ameter into an electric magnitude inversely propor- {581 Field of Search l39f97, 99, 107, 108, lit); tional to such diameter; detecting and transforming at 66:!86 A; 318;6 least the tension variations of the warp into an electric amplitude proportional thereto; conducting the rotary {56} References Cited speed of said electric motor with these three electric UNITED STATES PATENTS magnitudes in such a manner that this speed remains constantly inverseiy proportional to the pick density 333;; g ggg gggg;;;;;-------- 5,353 and m the diameter of the thread that and that this 3674369 441954 Bassish" M 66/36 A speed changes in the same direction as the said ten- 2 37 35 2 1959 Bassis; H 139/193 X sion variations of the warp, during normal operation 2,627,592 211953 Hutton et al 318/6 0f the loom. 3,489.96! 1/1970 Hank 31816 3,368,854 321967 lfarrwaiier 139 99 9 Claims 4 Drawing Figures PAYENTEU APR 9 I974 SHEET 1 0F 4 PATENTED APR 9 I974 SHEET 3 (IF 4 n SR summons 9 Ian 3, 802.467

saw u a? a WAR? UNWlNDER FOR WEAVING LOOMS The present invention covers a process for warp let off from a thread shaft in a weaving loom and a warp unwinder for performing such process.

The unwinding of the warp on a weaving loom is still stating a problem which continues to call forth difficulties for winding loom designers and manufacturers, owing to the fact that it has not been soived so far in a quite satisfactory way.

indeed, notwithstanding the skill that has already been displayed in this field, none of the available systems can pride itself on perfection: all of them are still subject to more or less important defects and drawbacks and only solve the problem in a more or less approximate way.

Moreover, the new present day textile fibres, the constant need for higher production and output, more stringent exigencies as regards improved quality of fabrics, etc. require mechanisms or systems working less approximately and striving after perfection.

That is the reason why present endeavours are still aimed at improving the available mechanisms or designing completely new equipments and systems. The number of patents handed in for this purpose sufficiently evidences this fact.

The warp let off is usually performed through rotation of the warp shaft or thread shaft, which is normally set up at the rear of the loom. As the production of the fabric increases, the diameter of the warp shaft is reduced and, owing to the fact that the length of the yielded thread must remain strictly constant, this implies that the shaft speed must be stepped up as the warp shaft diameter decreases.

The thread delivery depends simultaneously on the pick density or, in other words, on the number of shoots per length unit of the fabric and on the interweaving i.e. the] additional warp length which it is necessary to yield on the length of the fabric obtained. The interweaving proceeds from the undulations made by the warp thread to shape the fabric. This depends on a large number of parameters, to such extent that it is not possible to reckon the interweaving with sufficient accuracy in order to have it intervene in the mechanism (f.i. in the shape of a cog-wheel transmission or similar). The latter is therefore an unknown.

It is possible to show that the rotary speed of the warp shaft:

1. must be inversely proportional to its diameter,

2. must be inversely proportional to the pick density, 3. must be directly proportional to (l E), in which E represents the interweaving, expressed in decimals.

It is now established that the warp must be tightened during the weaving process. in order to avoid stripes in the manufactured fabric, it is necessary to maintain the warp tension as constant as possible. Since the advance of the fabric is regular, the constancy of the warp tension only depends on the unwinding process; if the tension diminishes, this is due to the fact that the unwinding is too important; on the other hand, if the tension increases, this is due to the fact that the delivery is inadequate. This circumstance is habitually used to regulate the warp unwinding by checking its tension. However, it is also usual to require too much of such regulation system: one confines oneself to an approximate unwinding motion and the regulation is expected to do the rest. That is a mistake, because it causes still higher tension fluctuations than required and sometimes even a progressive tension fluctuation from the head to the end of the shaft.

The subject of this invention consists of a process for warp let off as well as an unwinder of an entirely new design, which enables to obtain perfect unwinding. This is achieved, according to the invention, by applying a process mainly consisting in: transforming the motion of a movable part of the pulling gear into an electric magnitude inversely proportional to the pick density, transforming continuously the diameter of the thread shaft into an electric magnitude inversely proportional to such diameter, detecting at least the warp tension variations and transforming them into an electric magnitude proportional therewith, conducting the rotary speed of the said electic motor by means of these three electric magnitudes in such manner that this speed remains constantly inversely proportional to the shoot density and with the thread shaft diameter and that this speed further changes in the same direction as the said warp tension variations during normal operation of the loom.

in this way the rotary speed of the warp shaft adapts itself automatically both to the diameter and to the shoot density obtained as well as to the interweaving. Therefore the tension can be kept within extremely stringent limits which have not been achieved so far, and consequently remains particularly constant.

In a plant where this new process is applied, in case the interweaving is nil, the unwinding process is performed in such way that the regulating system remains theoretically inactive by means of the tension. The working load of the regulating system is therefore reduced to a minimum; it merely influences the unwinding in function of the interweaving and with the slight casual tension fluctuations due for instance to the shearing irregularities.

Moreover this unwinder can be operated in backflow just as in normal working.

This unwinder further keeps the warp tension constant during the stoppages of the loom; to such purpose it will do to feed the electric part. When, for instance after stoppage during the night or the week-end, the loom motor is started, the unwinder will restore the warp tension and bring it back to its correct value, because during this long stoppage the alterations in the ambient atmospherical conditions (temperature, moistness) have influenced the warp and altered its tension. The weaving loom may therefore be started with a warp tension which is exactly the same as the one prevailing when the loom was stopped. This process avoids stripes on the fabric. All unwinding devices known to this day improve such tension fluctuations only after a more or less long operation (according to their sensitiveness) and therefore cause a defect which is visible on many fabrics.

The unwinder referred to hereabove adapts itself to strongly varying deliveries, thus affording the weaving of an ample range of fabrics.

The warp tension of this unwinder can be regulated very easily to a quite large extent.

The winding process is then uninterrupted and therefore not intermittent as with most of the available systerns.

The unwinder adapts itself to all looms, but in point of fact this adaptation is easier on looms on which the advance of the fabric in uninterrupted and not intermittent.

The mechanical part of this unwinder has been reduced to the utmost; the warp shaft is driven by an elec tric motor with variable speed through the medium of a reduction gear constaining at least one worm wormwheel torque, so as to warrant the irreversibility of the system.

The main part of this unwinder is of course this part, which controls the speed of the electric motor. This control is carried out electronically and can be performed in different ways, starting from a single and same basic principle. in other words, the basic principle of this unwinder is liable to lead to different designs, according to the means used.

The basic principle of this unwinder consists in recording at various suitable points three kinds of data referring respectively to the shoot density obtained, the warp shaft diameter and the warp tension, in processing such data and in causing them to cooperate in such a manner that under their influence the rotary speed of the motor and consequently that of the warp shaft be inversely proportional at any moment to the shoot density obtained, inversely proportional to the warp shaft diameter and in addition is influenced in the correct direction by the fluctuations of the warp tension.

The means used with a view to reaching this end may vary according to the nature of the electric motor used, the nature of the data recorders, the data processing method(s) chosen, etc.

in order to clarify the above comments, we are itemizing below, as an information, one of the achievements according to the invention, as well as several alternatives to which this achievement lends itself, with relative reference to the attached diagrammatic drawings.

FIG. 1 shows the fundamental diagram of the mechanical part of the unwinder and of the location of the various data collectors on the weaving loom.

FIG. 2 shows the itemized block diagram of an application form of the invention, which does not make allowance for the backflow.

FIG. 3 shows a block diagram similar to that of FIG. 2, which however makes allowance for a backflow.

FIG. 4 shows a special feature of the motor feed in case a backflow is provided for.

With reference to FIG. 1, warp l unwinds from shaft 2 and first passes on a fixed roller 3, then to a roller 4 before arriving at the heddles 5, which constitute the compartment. The fabric 6 is formed at feel 7 of the fabric and is regularly pulled forward by roller 8 which is usually called sand roller. The latter is driven from the lower spindle 9 of the weaving loom, which carries a screw-shaped cog-wheel 10, which interlocks with another screw-shaped cog-wheel 11, secured on a spindle 12. The rotary motion of this spindle I2 is transmitted by the cog-wheel l3, l4, l and 16 to a spindle 17, on which a worm 18 is secured, which drives a wormwheel 9, which in turn drives a cog-wheel 20, the latter interlocking with a wheel 21 which is secured on the spindle of the sand roller 8. The cog-wheels l3, 14, and 16 determine the number of shots per length unit of the fabric, i.e. the pick density and are therefore usually indicated under the name of "shooting wheels". It will do to change one or several shooting wheels in order to modify the pick density.

On spindle 17 a cog-wheel 22 is also secured and a magnetic recorder 23 is located close to the cogs of this cog-wheel. Every cog positioned before this recorder will act on the latter and the regular and uninterrupted rotary motion of wheel 22 will therefore induce an alternating current in this recorder, whose frequency is dependent on the pick density obtained, and more ac curately, inversely proportional to this pick density.

It is obvious that the magnetic recorder 23 may be substituted by an optical recorder for instance, which reacts under the action of the beams emitted by a source of light and are reflected in the cogs or pass through the cog cavities. The cog-wheel 22 may in such case be substituted by a disc with holes and chinks or also with alternative reflecting and non-reflecting parts.

The whole wheel recorder may also be substituted by a small alternator.

in a general way, any system may be adopted which is capable of transforming a rotary motion into an electric magnitude inversely proportional to the pick density.

This system should be set up between the shot wheels or an equivalent system and the sand roller, and preferably of the spindle whose rotary speed is highest. In this way, a modification of the shot wheels causes automati cally, in this realization instance, an alteration of the induced current frequency. When the loom is stopped, there is no more induced current and consequently the frequency is nil.

A shaft feeler, consisting for instance of a lever 24 rotating around a spindle 25 and provided at its free end with a roller (or shoe) 26, constantly kept in contact with the warp threads on the warp shaft through the action of spring 27, controls, by means of a multiplier with cog-wheels 28-29 a recorder 30 which, in the case considered, is nothing else but a potentiometer with linear characteristic, whose resistance is proportional to the diameter of the warp shaft. The current that passes through the potentiometer under constant tension is then inversely proportional to the warp shaft diameter.

It is obvious that in such case one may use any system that is capable of constantly keeping an electric magnitude inversely proportional to the warp shaft diameter.

The warp shaft scanner may, instead of pivoting or rotating around a spindle, also be a scanner with rectilinear radial shifting; in such case the transmission of the motion is carried out with a toothed cramp and cogwheel.

Roller 4, on which warp 1 runs, it shown fixed in the case illustrated on diagram 1. A warp tension fluctuation results in a variation of the pressure exerted by bearings 31 of the roller on their anchoring pedestal 32. A pressure recorder 33, such as a piezo-quartz or ditto ceramic for instance, positioned between the bearings and the pedestal, will react on such variations and will afford a paramter (tension and/or current) which at any moment is proportional to the warp tension.

Roller 4 may also be movable as in all mechanical unwinders; the pressure recorder would in such case be substituted by a displacement recorder.

Generally speaking, one may use any system that is capable of changing an electric magnitude proportional to the warp tension and/or its variations.

Due to the fact that the warp is subject to cyclical tension variations, which are chiefly ascribable to the crossing and the opening of the compartment, it will do to integrate the variable diameter, which is supplied by recorder 33, using notorious means for this purpose in order to obtain its mean value, rid of the cyclical fluctuations. This mean value corresponds with the mean value of the warp tension.

The rotary motion of warp shaft 2 is obtained by an electric motor 34 through the medium of a reduction consisting of the cog-wheels 35 (secured on the motor spindle end) 36, 37, 38 and the worm 39, which interlocks with wheel 40, which is secured on the warp shaft spindle.

In this execution instance, the electric motor 34 is a direct current motor with constant field. Therefore, its speed under constant load is only dependent on the power fed to it.

It is notorious that a modern conducting process for motors of this type consists in feeding them with current impulses, in the manner of a switch which is continuously opened and closed, this switch being, in the case under consideration, a notorious electric device. The power fed to the motor then depends simultaneously on the shape of the impulsions, on their amplitude, on their frequency and on their duration in respect of their period (inversed as regards the frequency). It is obvious that, in case one or several of these parameters are modified, the speed of the motor can also be easily altered simultaneously.

in this example of realization, the impulses incumbent on the motor have a rectangular shape. Their frequency is inversely proportional to the pick density and their duration inversely proportional to the warp shaft diameter. Such impulses are obtained from the electric connections controlled by the recorders 23 and 30.

The comprehensive device is designed in such manner that, in case of an interweaving default, the warp length afl'orded by the warp shaft is exactly equal to the length of the fabric obtained. In such case unwinding is mathematically correct; however, due to the fact that the interweaving is practically never nil, the delivery will actually be slightly too small and the warp tension will slightly increase.

At that moment recorder 33 comes into action and provides the motor with a little additional direct current, which, added to the impulses, increases the motor speed in the required proportion. In order that this speed increase should be proportional to the momentary speed of the motor or, in other words, in order that the relative speed increase should be constant for the same interweaving, the additional current is set proportionally to the mean value of the impulses.

The relative speed increase adapts itself automatically to the (unknown) value of the interweaving and is of course influenced by the casual tension variations of the warp.

The suggested solution can be mathematically expressed as follows:

D, diameter of sand roller 8 in cm.

D diameter of warp shaft 2 in cm.

P pick density (number of shots per fabric length unit) in shots per cm. expressed in decimals E inverweaving R, total transmission ratio between sand roller 8 and cog-wheel 22 R total transmission ratio between driving motor 34 and warp shaft 2 (both these ratios are taken in the same dirction higher than I).

Z number of cogs of wheels 22 f= number of periods per shot in recorder 23 N number of revolutions per shot of motor 34 t impulse time A revolution of sand roller 8 corresponds to:

rrD cm. fabric 11D, (1 E) cm warp and 1r.D .P shots Consequently: N X rr .D .P/R=) X 17.0; 1r.D (l+E) and N R lrr .D P) (l+E) on the other hand:

f= (R,.Z)!(1r.D .P) of which P =(R .Z)/(1r.D .fl

and t k/D of which D k]:

in which k is a constant dependent on the electronic connection.

in case P and D are substituted by their value in comparison (I), one obtains:

N (D,,.R,)/(k.Z.R,) .f.t(l E), viz. presuming (D .R )/(k.Z.R q(=constant):

Comparison (1 indicates that the motor speed is inversely proportional both to the pick density P and to the warp shaft diameter D; and directly proportional to (HE).

Comparison (2) determines the connection between the pick density P and the frequency of the alternative current induced in recorder 23, whereas comparison (3) expresses the connection between the warp shaft diameter D and the impulse time.

Comparison (4) indicates that the motor speed is simultaneously proportional to f. to r and to (l-l-E).

in comparison (5) the first term of the second member corresponds with the speed generated by the impulses, while the second term corresponds with the speed increase caused by the direct current component. The latter term indicates that the speed increase is proportional not only to the interweaving E, but also to f and r, as already explained previously. The casual tension variations of the warp influence this last term only.

Reference is now made to the block diagrams of FIGS. 2 and 3, which differ from each other merely through the addition in the second diagram of a backflow system, which does not appear in the first one.

In the recorder 23 an alternative current (or pulsed current) is induced with a frequency that it is inversely proportional to the pick density. The amplitude of this current also varies according to the pick density and the shape of its wave depends on the type of recorder used and on the wheel 22.

In order to afford a very accurate check, the useless and disturbing variables must be ruled out. The current of recorder 23 is therefore applied at the inlet of a monostable tipping switch 41.

It is notorious that this electronic device can be placed in two conditions, one of them stable and the other one unstable. A suitable impulse at tbe inlet of the reversing switch causes it to tip into its unstable condition. It comes back automatically to its stable condition after a certain time, depending on the value of some of its constituent elements. In the contemplated execution, this time is provided so as to be slightly shorter than the period of a maximum frequency. This slight difference is required for interrupting the thyristors current (see further on).

The tipping switch 41 is connected with a capacity booster 42, fed by feeder 43, the outlet of which is connected with a thyristor conducting block 44 and with the anod of at least one thyristor 45. Recorder 30 is also connected with conducting block 44.

In this manner every current period of recorder 23 causes the monostable switch 41 to tip into its unstable condition; it comes back to its stable condition before the action of the second period and gives at its outlet some impulses of rectangular shape, with constant amplitude, constant duration and a frequency equal to the inlet impulses.

The rectangular impulses obtained are now reinforced for the purpose of giving them the required capacity and are then conducted to the motor via the thyristor (or a set of thyristors connected in parallel). The capacity is obtained by a feeding block which is known as such.

it is notorious that the thyristor is a conducted diode, which becomes conductive or, in other words, which allows a current to pass only when a suitable impulse is sent to its conducting electrode. The current in the thyristor is interrupted automatically as soon as the tension falls under a certain value which depends on the type of thyristor.

It is understandable that the current in the thyristor will be interrupted at the end of every impulse and that it is sufficient to cause the thyristor to become conductive at a variable moment between the beginning and the end of the impulse to allow only a more or less large portion of this impulse i.e. of a more or less long duration, to pass, in order to alter in this way the fed power and consequently the motor speed.

For this purpose, a conducting block supplies the impulses required for making the thyristor conductive. Such impulses are generated by a well-known process from a linking with variable time constant. Such time constant is conducted by recorder 30, i.e. in fact by the warp shaft diameter.

When the warp shaft 2 is filled, the thyristor becomes conductive comparatively late, so that only a small portion of the capacity impulse arrives in motor 34. Therefore the latter rotates slowly. in proportion as the diameter of warp shaft 2 becomes smaller, thyristor 45 is made conductive sooner, the fed power increases and motor 34 quickens its speed.

The rotary speed of motor 34 changes simultaneously and dependent on the number of impulses which the motor receives (pick density) and in relation to the duration of such impulses (diameter of warp shaft).

The conducting block 44 of the thyristor (of the thyristors 45) is regulated to such extent that, when the proportion between the diameter of the full and the diameter of the empty warp shaft 2, for instance is equal to 6, the portion of the impulse which motor 34 receives at the outset of the warp shaft only reaches one sixth of the impulse portion it receives at the end of the warp shaft.

On the other hand, the capacity reinforcement 42 is adjusted so that the delivery of the warp shaft 2 is mathematically correct in case there is no interweaving.

If the weaving loom is equipped with a backflow system, either mechanical or electro-magnetic, a changeover switch 46 enables to alter the direction of the current throughflow in the motor anchor so that the rotary direction of motor 34 is changed over.

Four thyristors 45a, 45b, 45c, 45d, arranged as shown on diagram 4, are then required. in the condition shown on this diagram, the thyristors 45b and 45c only can be made conductive and then the current is introduced into the motor from the bottom to the top (the direction of the current used here is the conventional direction from positive to negative). Now, in case the condition of switch 46 is modified, the conductive making impulses only reach the thyristors 45a and 45d and the current is introduced into the motor from the top to the bottom.

As shown on diagram 4, the change-over switch 46 may be a mere double direction switch, set up on the passage of the conductive making impulses and actuated for instance by the lever of the backflow device in case its nature is mechanical, or by a small relay in case its nature is electro-magnetic. This change-over switch may even be purely electronic.

On the other hand, the warp tension and its fluctuations call forth in recorder 33 a current and/or a tension with fluctuations of even nature, which is placed at an integrating circuit 47, which restores its mean value and thus eliminates any cyclical fluctuations.

This mean value is then compared, in 48, with a fixed reference value 49. In this case, to compare means to make the difference. Considering that, the interweaving being nil, the delivery of the warp shaft is mathematically correct, the difference would also be nil in this case. In fact, this difference would oscillate around the nil value depending on the casual tension modifications.

Considering that the interweaving is never nil, and since the warp shaft delivery must necessarily adapt itself to this state of things, the difference will take a given (mean) value that will be at the origin of the additional direct current fed to the motor.

As already shown hereabove -(see comparison 5) this additional current (and in a more general way its mean value must be proportional not only to the interweaving but also to the mean value of the impulses, in order that the relative speed increase of motor 34 be constant for a given interweaving.

To such end, a very small portion of the impulses feeding the motors is sent at thyristor (or thyristors) 45 outlet into an integrating circuit 50, which restores its mean value. in case the weaving loom is provided with a backflow system, the outlet of integrating circuit 50 is connected with a rectifier bridge 51 so that, whatever the direction of the impulses, their mean value always keeps the same direction.

This mean value is then sent to a capacity booster 52 with sensitiveness regulation 53, which is fed by a wellknown feeding block 54, which moreover receives the difference between the mean value of the tension and the reference value. The reinforcement of the difference is thus modulated by the mean value of the im' pulses, and booster 52 gives at its outlet a current which is proportional to both these parameters. This current is set at the connection terminals of motor 34 and superposes itself to the impulses with a view to modifying the motor speed in this way.

if only the interweaving is considered, it always causes a speed increase, same as a tension increase. Therefore the mean tension value is slightly higher than the reference value; to express it in conventional terms, the difference is positive.

A casual tension drop, if it is substantial enough, is liable to reverse the meaning of the difference, causing this difference to become negative. For this reason the booster S2 is designed in such manner that in such cases the direction of the current it supplies also changes over. This current is then substracted from such impulses and slows down the motor.

It will be readily understood that, according to the amplitude of the reinforcement, motor 34 will react more or less quickly to the fluctuations of the warp tension. Thus the regulation 53 of the reinforcement enables to modify the sensitiveness of the warp unwinder.

[t is also sufficient to make the reference value 48 adjustable in order to regulate the warp tension simultaneously.

When the loom stops, the wheel 22 also comes to a stop and in consequence thereof the generation of impulses is interrupted. Owing to the fact that there are no more impulses, motor 34 itself also stops. The mean value of non-existent impulses is necessarily nil and the last booster 52 would be blocked if, upon stoppage, this mean value would not be substituted by any fixed value (which may be for instance the reference value), enabling the booster to react to the warp tension fluctuations, in case of default of impulses, and to feed a current to the motor which enables this motor to improve and eliminate the tension fluctuations.

This fixed substitution value can be sent to booster 52 by means of a small switch 55, which closes when the loom stops for instance through the action of the coupling lever in case of mechanical drive or through the action of a small relay in case of an electromagnetic driving system. This switch 55 may also be of a purely electronic nature.

in order to prevent motor 34 from continuing to rotate during a moment under the influence of its inertia and with a view to stopping the motor at once upon stoppage of the weaving loom, it is advisable to apply a braking system with momentary action on the motor. Several systems can be contemplated for such purpose, namely for instance an electro-magnetic brake that acts on the motor spindle and is fed by a well-known electronic linking which, upon stoppage of the weaving loom, sends a single current impulse in the brake spool, the amplitude and duration of which are sufficient to practically stop the motor.

What I claim is:

1. Process for warp let off from a warp beam in a weaving loom with take up device and in which the warp beam is driven by an electric motor, comprising the steps of transforming the motion of a movable part of the take up device into an electric magnitude in versely proportional to the pick density; transforming continuously the warp beam diameter into an electric magnitude inversely proportional to such diameter; detecting and transforming at least the tension variations of the warp into an electric amplitude proportional thereto; conducting the rotary speed of said electric motor with these three electric magnitudes in such a manner that this speed remains constantly inversely proportional to the pick density and to the diameter of the warp beam and that this speed changes in the same direction as the said tension variations of the warp, during normal operation of the loom.

2. Process according to claim 1, wherein the electric magnitude into which the warp tension variations are transformed is also maintained proportional to the m0- mentary motor speed.

3. Device for warp let off from the warp beam in a weaving loom with take up device and in which the warp beam is driven by an electric motor, comprising the combination of means aimed at transforming the motion of a movable part of the take up device into an electric magnitude inversely proportional to the pick density; means for continually transforming the warp beam diameter into an electric magnitude inversely proportional to such diameter, means for detecting and transforming at least the warp beam variations into an electric magnitude proportional to it and means for conducting the rotary speed of said electric motor on the basis of the three said electric magnitudes in such a manner that such speed remains constantly inversely proportional to the pick density and to the warp beam diameter and that such speed further changes in the same direction as the said warp tension variations, during normal operation of the loom.

4. Device according to claim 3, including means for also maintaining the electric magnitude into whiclh the warp tension variations are transformed proportional to the momentary motor speed.

5. Warp unwinder according to claim 3, for a weaving loom in which the warp beam spindle is driven by an electric motor with variable speed, said unwinder being equipped with three separate recorders, respectively influence by the pick density, the warp beam diameter and the tension and/or tension fluctuations of the warp, while the outlet signals of such recorders determine simultaneously the rotary speed of the motor.

6. Warp unwinder according to claim 5, wherein said recorder which is influenced by the pick density consists of a magnetic recorder, placed near the cogging of a cog-wheel provided for such purpose and which is secured on the spindle of one of the usual shot wheels of the loom.

7. Warp unwinder according to claim 4, wherein said recorder which is influenced by the warp shaft diameter, consists of a potentiometer controlled by the motion of a shaft scanner.

8. Warp unwinder according to claim 4, wherein said recorder which is influenced by the tension and/or tension fluctuations of the warp, consists of a pressure recorder, placed under in fixing pedestal of the bearings of a conducting roller on which the warp runs.

9. Warp unwinder according to claim 3, wherein said motor is a direct current motor with constant field.

# i i l i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,802,467 Dated April 9, 1974 Patent No.

Bernard Charles-Louis Steverlynck Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The assignee should read Weefautomaten Picanol Signed and sealed this 24th day of September 197 (SEAL) Attest:

C. MARSHALL DANN McCOY M. GIBSON JR. Attesting Officer Comissioner of Patents 

1. Process for warp let off from a warp beam in a weaving loom with take up device and in which the warp beam is driven by an electric motor, comprising the steps of transforming the motion of a movable part of the take up device into an electric magnitude inversely proportional to the pick density; transforming continuously the warp beam diameter into an electric magnitude inversely proportional to such diameter; detecting and transforming at least the tension variations of the warp into an electric amplitude proportional thereto; conducting the rotary speed of said electric motor with these three electric magnitudes in such a manner that this speed remains constantly inversely proportional to the pick density and to the diameter of the warp beaM and that this speed changes in the same direction as the said tension variations of the warp, during normal operation of the loom.
 2. Process according to claim 1, wherein the electric magnitude into which the warp tension variations are transformed is also maintained proportional to the momentary motor speed.
 3. Device for warp let off from the warp beam in a weaving loom with take up device and in which the warp beam is driven by an electric motor, comprising the combination of means aimed at transforming the motion of a movable part of the take up device into an electric magnitude inversely proportional to the pick density; means for continually transforming the warp beam diameter into an electric magnitude inversely proportional to such diameter, means for detecting and transforming at least the warp beam variations into an electric magnitude proportional to it and means for conducting the rotary speed of said electric motor on the basis of the three said electric magnitudes in such a manner that such speed remains constantly inversely proportional to the pick density and to the warp beam diameter and that such speed further changes in the same direction as the said warp tension variations, during normal operation of the loom.
 4. Device according to claim 3, including means for also maintaining the electric magnitude into whiclh the warp tension variations are transformed proportional to the momentary motor speed.
 5. Warp unwinder according to claim 3, for a weaving loom in which the warp beam spindle is driven by an electric motor with variable speed, said unwinder being equipped with three separate recorders, respectively influence by the pick density, the warp beam diameter and the tension and/or tension fluctuations of the warp, while the outlet signals of such recorders determine simultaneously the rotary speed of the motor.
 6. Warp unwinder according to claim 5, wherein said recorder which is influenced by the pick density consists of a magnetic recorder, placed near the cogging of a cog-wheel provided for such purpose and which is secured on the spindle of one of the usual shot wheels of the loom.
 7. Warp unwinder according to claim 4, wherein said recorder which is influenced by the warp shaft diameter, consists of a potentiometer controlled by the motion of a shaft scanner.
 8. Warp unwinder according to claim 4, wherein said recorder which is influenced by the tension and/or tension fluctuations of the warp, consists of a pressure recorder, placed under a fixing pedestal of the bearings of a conducting roller on which the warp runs.
 9. Warp unwinder according to claim 3, wherein said motor is a direct current motor with constant field. 